1. Field of the Invention
This invention relates generally to dynamic test fixtures, and more particularly to a test fixture for a miniature space craft for simulation and testing of thrust devices and controls.
2. Description of Related Art
The following art defines the present state of this field:
Simon, U.S. Pat. No. 3,225,608 describes a diamagnetic suspension apparatus including a body of diamagnetic material; an inhomogeneous magnetic field volume which is symmetrical about the longitudinal axis thereof, the field intensity within the volume increasing rapidly with the radial distance from the longitudinal axis, the field intensity also increasing rapidly with the distance along the longitudinal axis in a predetermined direction, the diamagnetic body being normally freely suspended within the volume in a position which is substantially symmetrical about the axis.
Dukes et al., U.S. Pat. No. 3,370,205 describes a magnetic suspension system for supporting in a substantially invariant orientation of a magnetizable suspended body whose position may vary comprising, in combination a system of three sets of magnetic-field-producing (m.f.p.) elements, said sets arranged to produce three orthogonal magnetic forces which suspend the body and control its movement with respect to three orthogonal axes, the magnetic force component produced by each set being a function of an electrical parameter in such a way that the average value of said parameter is that required to position said suspended body at its nominal equilibrium point, position-sensing means for detecting changes in position of said suspended body along said three orthogonal axes and for providing signals proportional in value to said changes, and feedback control means for utilizing each of said change-proportional signals to vary the value of said parameter in the proper set of m.f.p. elements to produce the compensatory change in its field strength required to return said body to its nominal equilibrium point along the axis associated with that set of m.f.p. elements.
Fischell et al., U.S. Pat. No. 4,170,904 describes an improved system for sensing and compensating for external disturbance forces acting on a satellite while in orbit. A proof mass member is housed within an enclosure and shielded from external, non-gravitational forces. The proof mass is electromagnetically levitated to move in a purely gravitational orbit, along an axis aligned with the satellite""s velocity vector. The proof mass is subjected to a controlled magnetic biasing field and is caused to have a constant reaction to the resultant biasing force, by means of a thermal control system which maintains constant resistivity of the proof mass, during operation. The position of the proof mass with respect to its axis is detected optically and is utilized to control the firing of spacecraft thrusters. As a result, the satellite is caused to maintain a substantially constant position relative to the proof mass and thereby also is caused to follow a purely gravitational orbit.
Ozols, U.S. Pat. No. 4,648,273 describes a device for detecting the influence of a gravitational force on a body due to changes in a freefall state. The device includes a spherical housing, and a flow medium is contained in, and is adapted to travel about and undergo flow in the housing. Monitoring means are provided at presence or absence of medium at said positions.
Lordo et al., U.S. Pat. No. 4,908,558 describes a flight motion simulator including a unit under test supported on a stationary frame for angular and translational movement along pitch, roll, and yaw axes. A rotor element is secured to the unit under test and has a spherical configuration. Magnetic bearings supported by the stationary frame support the rotor element in three degrees of freedom of movement. A drag-cup induction motor is mounted on the frame and connected to the unit under test to generate three degrees of freedom of movement by generating a rotating magnetic flux in a stator assembly to induce a corresponding flow of currents in the rotor element to produce torque and motion in the unit under test in the same direction as the flux movement in the stator assembly.
Tozoni, U.S. Pat. No. 5,319,275 describes a magnetic levitation self-regulating system having enhanced stabilizational forces designated for immobile, or forward, or rotational motion and stable hovering of heavy masses (working bodies) in both gravity and weightlessness are proposed. This system includes a stator assembly and a levitator assembly. The stator assembly comprises split iron cores with air gaps between their core shoes fixed on a non-magnetic foundation and magnetic screens in the capacity of which serve superconductive, or permanent magnetic, or nonmagnetic conductive strips. The levitator assembly comprises permanent magnets couplet together by non-magnetic couplers and disposed into the air gaps of the stator assembly. The levitator magnets are magnetized across the air gaps of the stator and generate the primary magnetic field, magnetizing the iron cores, which, in turn, create a secondary magnetic field. The magnetic screens change distribution of the primary and secondary magnetic fields in the air gaps. The resulting magnetic field creates a stabilizational forces providing a stable hovering of the levitator without any active control system and additional energy sources.
Zeamer, U.S. Pat. No. 5,485,748 describes a magnetically levitated force/weight measurement apparatus including a system core with a plurality of layered circular segments having apertures that define an internal chamber. The segments include, inter alia, upper and lower magnetic bearing segments, a coil segment and an optical detector segment, each of which cooperate to generate magnetic fields for levitating a mass disposed within the chamber. Levitation magnets, rigidly disposed within the mass along a center axis, are arranged such that similar poles are in facing relation. This novel arrangement generates a static magnetic field that radiates orthogonally and symmetrically from the mass and generates a force vector for levitating the mass along the center axis. Bearing magnets, disposed within the magnetic bearing segments, i.e., core bearing magnets, and the spool, i.e., spool bearing magnets, are also arranged such that the polar axes of the core bearing magnets are aligned in the same direction as the polar axes of their corresponding spool bearing magnets. A self-dampening optical and current feedback system ensures that, upon displacement of the spool along the center axis, the spool returns to a stable equilibrium position.
The prior art teaches magnetic suspension and levitation systems, simulators of various types, force responsive devices, disturbance compensation systems, and force/weight measurement systems. However, the prior art does not teach that a spacecraft motion simulation device may be constructed in accordance with the present instruction or used with a closed loop camera system. The present invention fulfills these needs and provides further related advantages as described in the following summary.
The present invention teaches certain benefits in construction and use which give rise to the objectives described below.
The present invention provides a spacecraft motion simulation device providing up to four degrees of freedom of motion to a test article and enables viewing a picture on a projection screen from a camera within the test article. One or more of such pictures may be moved during the test and the test article may be thus also moved in accordance with the testing of controls and thrusters on the test article. Closed loop control of the test article may be achieved using attitude control circuits for adjusting test article position and attitude relative to recognized elements within the projected screens.
A primary objective of the present invention is to provide a spacecraft motion simulation device having advantages not taught by the prior art.
Another objective is to provide near friction free support and frictionless levitation to a test article through a test fixture.
A further objective is to provide a means for viewing scenes from the test article so as to judge the effectiveness of test article thrust controls as well as the efficiency of the control system.
A further objective is to provide a means for achieving closed loop control of the test article by using attitude control circuits for adjusting test article position and attitude relative to recognized elements within the projected screens.